<?php
/**
 * CodeIgniter
 *
 * An open source application development framework for PHP
 *
 * This content is released under the MIT License (MIT)
 *
 * Copyright (c) 2014 - 2017, British Columbia Institute of Technology
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 *
 * @package	CodeIgniter
 * @author	EllisLab Dev Team
 * @copyright	Copyright (c) 2008 - 2014, EllisLab, Inc. (https://ellislab.com/)
 * @copyright	Copyright (c) 2014 - 2017, British Columbia Institute of Technology (http://bcit.ca/)
 * @license	http://opensource.org/licenses/MIT	MIT License
 * @link	https://codeigniter.com
 * @since	Version 2.0.3
 * @filesource
 */
defined('BASEPATH') or exit('No direct script access allowed');

/**
 * SQLSRV Database Adapter Class
 *
 * Note: _DB is an extender class that the app controller
 * creates dynamically based on whether the query builder
 * class is being used or not.
 *
 * @package CodeIgniter
 * @subpackage Drivers
 * @category Database
 * @author EllisLab Dev Team
 * @link https://codeigniter.com/user_guide/database/
 */
class CI_DB_sqlsrv_driver extends CI_DB
{

    /**
     * Database driver
     *
     * @var string
     */
    public $dbdriver = 'sqlsrv';

    /**
     * Scrollable flag
     *
     * Determines what cursor type to use when executing queries.
     *
     * FALSE or SQLSRV_CURSOR_FORWARD would increase performance,
     * but would disable num_rows() (and possibly insert_id())
     *
     * @var mixed
     */
    public $scrollable;
    
    // --------------------------------------------------------------------
    
    /**
     * ORDER BY random keyword
     *
     * @var array
     */
    protected $_random_keyword = array(
        'NEWID()',
        'RAND(%d)'
    );

    /**
     * Quoted identifier flag
     *
     * Whether to use SQL-92 standard quoted identifier
     * (double quotes) or brackets for identifier escaping.
     *
     * @var bool
     */
    protected $_quoted_identifier = TRUE;
    
    // --------------------------------------------------------------------
    
    /**
     * Class constructor
     *
     * @param array $params            
     * @return void
     */
    public function __construct($params)
    {
        parent::__construct($params);
        
        // This is only supported as of SQLSRV 3.0
        if ($this->scrollable === NULL) {
            $this->scrollable = defined('SQLSRV_CURSOR_CLIENT_BUFFERED') ? SQLSRV_CURSOR_CLIENT_BUFFERED : FALSE;
        }
    }
    
    // --------------------------------------------------------------------
    
    /**
     * Database connection
     *
     * @param bool $pooling            
     * @return resource
     */
    public function db_connect($pooling = FALSE)
    {
        $charset = in_array(strtolower($this->char_set), array(
            'utf-8',
            'utf8'
        ), TRUE) ? 'UTF-8' : SQLSRV_ENC_CHAR;
        
        $connection = array(
            'UID' => empty($this->username) ? '' : $this->username,
            'PWD' => empty($this->password) ? '' : $this->password,
            'Database' => $this->database,
            'ConnectionPooling' => ($pooling === TRUE) ? 1 : 0,
            'CharacterSet' => $charset,
            'Encrypt' => ($this->encrypt === TRUE) ? 1 : 0,
            'ReturnDatesAsStrings' => 1
        );
        
        // If the username and password are both empty, assume this is a
        // 'Windows Authentication Mode' connection.
        if (empty($connection['UID']) && empty($connection['PWD'])) {
            unset($connection['UID'], $connection['PWD']);
        }
        
        if (FALSE !== ($this->conn_id = sqlsrv_connect($this->hostname, $connection))) {
            // Determine how identifiers are escaped
            $query = $this->query('SELECT CASE WHEN (@@OPTIONS | 256) = @@OPTIONS THEN 1 ELSE 0 END AS qi');
            $query = $query->row_array();
            $this->_quoted_identifier = empty($query) ? FALSE : (bool) $query['qi'];
            $this->_escape_char = ($this->_quoted_identifier) ? '"' : array(
                '[',
                ']'
            );
        }
        
        return $this->conn_id;
    }
    
    // --------------------------------------------------------------------
    
    /**
     * Select the database
     *
     * @param string $database            
     * @return bool
     */
    public function db_select($database = '')
    {
        if ($database === '') {
            $database = $this->database;
        }
        
        if ($this->_execute('USE ' . $this->escape_identifiers($database))) {
            $this->database = $database;
            $this->data_cache = array();
            return TRUE;
        }
        
        return FALSE;
    }
    
    // --------------------------------------------------------------------
    
    /**
     * Execute the query
     *
     * @param string $sql
     *            query
     * @return resource
     */
    protected function _execute($sql)
    {
        return ($this->scrollable === FALSE or $this->is_write_type($sql)) ? sqlsrv_query($this->conn_id, $sql) : sqlsrv_query($this->conn_id, $sql, NULL, array(
            'Scrollable' => $this->scrollable
        ));
    }
    
    // --------------------------------------------------------------------
    
    /**
     * Begin Transaction
     *
     * @return bool
     */
    protected function _trans_begin()
    {
        return sqlsrv_begin_transaction($this->conn_id);
    }
    
    // --------------------------------------------------------------------
    
    /**
     * Commit Transaction
     *
     * @return bool
     */
    protected function _trans_commit()
    {
        return sqlsrv_commit($this->conn_id);
    }
    
    // --------------------------------------------------------------------
    
    /**
     * Rollback Transaction
     *
     * @return bool
     */
    protected function _trans_rollback()
    {
        return sqlsrv_rollback($this->conn_id);
    }
    
    // --------------------------------------------------------------------
    
    /**
     * Affected Rows
     *
     * @return int
     */
    public function affected_rows()
    {
        return sqlsrv_rows_affected($this->result_id);
    }
    
    // --------------------------------------------------------------------
    
    /**
     * Insert ID
     *
     * Returns the last id created in the Identity column.
     *
     * @return string
     */
    public function insert_id()
    {
        return $this->query('SELECT SCOPE_IDENTITY() AS insert_id')->row()->insert_id;
    }
    
    // --------------------------------------------------------------------
    
    /**
     * Database version number
     *
     * @return string
     */
    public function version()
    {
        if (isset($this->data_cache['version'])) {
            return $this->data_cache['version'];
        }
        
        if (! $this->conn_id or ($info = sqlsrv_server_info($this->conn_id)) === FALSE) {
            return FALSE;
        }
        
        return $this->data_cache['version'] = $info['SQLServerVersion'];
    }
    
    // --------------------------------------------------------------------
    
    /**
     * List table query
     *
     * Generates a platform-specific query string so that the table names can be fetched
     *
     * @param
     *            bool
     * @return string
     */
    protected function _list_tables($prefix_limit = FALSE)
    {
        $sql = 'SELECT ' . $this->escape_identifiers('name') . ' FROM ' . $this->escape_identifiers('sysobjects') . ' WHERE ' . $this->escape_identifiers('type') . " = 'U'";
        
        if ($prefix_limit === TRUE && $this->dbprefix !== '') {
            $sql .= ' AND ' . $this->escape_identifiers('name') . " LIKE '" . $this->escape_like_str($this->dbprefix) . "%' " . sprintf($this->_escape_like_str, $this->_escape_like_chr);
        }
        
        return $sql . ' ORDER BY ' . $this->escape_identifiers('name');
    }
    
    // --------------------------------------------------------------------
    
    /**
     * List column query
     *
     * Generates a platform-specific query string so that the column names can be fetched
     *
     * @param string $table            
     * @return string
     */
    protected function _list_columns($table = '')
    {
        return 'SELECT COLUMN_NAME
			FROM INFORMATION_SCHEMA.Columns
			WHERE UPPER(TABLE_NAME) = ' . $this->escape(strtoupper($table));
    }
    
    // --------------------------------------------------------------------
    
    /**
     * Returns an object with field data
     *
     * @param string $table            
     * @return array
     */
    public function field_data($table)
    {
        $sql = 'SELECT COLUMN_NAME, DATA_TYPE, CHARACTER_MAXIMUM_LENGTH, NUMERIC_PRECISION, COLUMN_DEFAULT
			FROM INFORMATION_SCHEMA.Columns
			WHERE UPPER(TABLE_NAME) = ' . $this->escape(strtoupper($table));
        
        if (($query = $this->query($sql)) === FALSE) {
            return FALSE;
        }
        $query = $query->result_object();
        
        $retval = array();
        for ($i = 0, $c = count($query); $i < $c; $i ++) {
            $retval[$i] = new stdClass();
            $retval[$i]->name = $query[$i]->COLUMN_NAME;
            $retval[$i]->type = $query[$i]->DATA_TYPE;
            $retval[$i]->max_length = ($query[$i]->CHARACTER_MAXIMUM_LENGTH > 0) ? $query[$i]->CHARACTER_MAXIMUM_LENGTH : $query[$i]->NUMERIC_PRECISION;
            $retval[$i]->default = $query[$i]->COLUMN_DEFAULT;
        }
        
        return $retval;
    }
    
    // --------------------------------------------------------------------
    
    /**
     * Error
     *
     * Returns an array containing code and message of the last
     * database error that has occured.
     *
     * @return array
     */
    public function error()
    {
        $error = array(
            'code' => '00000',
            'message' => ''
        );
        $sqlsrv_errors = sqlsrv_errors(SQLSRV_ERR_ERRORS);
        
        if (! is_array($sqlsrv_errors)) {
            return $error;
        }
        
        $sqlsrv_error = array_shift($sqlsrv_errors);
        if (isset($sqlsrv_error['SQLSTATE'])) {
            $error['code'] = isset($sqlsrv_error['code']) ? $sqlsrv_error['SQLSTATE'] . '/' . $sqlsrv_error['code'] : $sqlsrv_error['SQLSTATE'];
        } elseif (isset($sqlsrv_error['code'])) {
            $error['code'] = $sqlsrv_error['code'];
        }
        
        if (isset($sqlsrv_error['message'])) {
            $error['message'] = $sqlsrv_error['message'];
        }
        
        return $error;
    }
    
    // --------------------------------------------------------------------
    
    /**
     * Update statement
     *
     * Generates a platform-specific update string from the supplied data
     *
     * @param string $table            
     * @param array $values            
     * @return string
     */
    protected function _update($table, $values)
    {
        $this->qb_limit = FALSE;
        $this->qb_orderby = array();
        return parent::_update($table, $values);
    }
    
    // --------------------------------------------------------------------
    
    /**
     * Truncate statement
     *
     * Generates a platform-specific truncate string from the supplied data
     *
     * If the database does not support the TRUNCATE statement,
     * then this method maps to 'DELETE FROM table'
     *
     * @param string $table            
     * @return string
     */
    protected function _truncate($table)
    {
        return 'TRUNCATE TABLE ' . $table;
    }
    
    // --------------------------------------------------------------------
    
    /**
     * Delete statement
     *
     * Generates a platform-specific delete string from the supplied data
     *
     * @param string $table            
     * @return string
     */
    protected function _delete($table)
    {
        if ($this->qb_limit) {
            return 'WITH ci_delete AS (SELECT TOP ' . $this->qb_limit . ' * FROM ' . $table . $this->_compile_wh('qb_where') . ') DELETE FROM ci_delete';
        }
        
        return parent::_delete($table);
    }
    
    // --------------------------------------------------------------------
    
    /**
     * LIMIT
     *
     * Generates a platform-specific LIMIT clause
     *
     * @param string $sql            
     * @return string
     */
    protected function _limit($sql)
    {
        // As of SQL Server 2012 (11.0.*) OFFSET is supported
        if (version_compare($this->version(), '11', '>=')) {
            // SQL Server OFFSET-FETCH can be used only with the ORDER BY clause
            empty($this->qb_orderby) && $sql .= ' ORDER BY 1';
            
            return $sql . ' OFFSET ' . (int) $this->qb_offset . ' ROWS FETCH NEXT ' . $this->qb_limit . ' ROWS ONLY';
        }
        
        $limit = $this->qb_offset + $this->qb_limit;
        
        // An ORDER BY clause is required for ROW_NUMBER() to work
        if ($this->qb_offset && ! empty($this->qb_orderby)) {
            $orderby = $this->_compile_order_by();
            
            // We have to strip the ORDER BY clause
            $sql = trim(substr($sql, 0, strrpos($sql, $orderby)));
            
            // Get the fields to select from our subquery, so that we can avoid CI_rownum appearing in the actual results
            if (count($this->qb_select) === 0) {
                $select = '*'; // Inevitable
            } else {
                // Use only field names and their aliases, everything else is out of our scope.
                $select = array();
                $field_regexp = ($this->_quoted_identifier) ? '("[^\"]+")' : '(\[[^\]]+\])';
                for ($i = 0, $c = count($this->qb_select); $i < $c; $i ++) {
                    $select[] = preg_match('/(?:\s|\.)' . $field_regexp . '$/i', $this->qb_select[$i], $m) ? $m[1] : $this->qb_select[$i];
                }
                $select = implode(', ', $select);
            }
            
            return 'SELECT ' . $select . " FROM (\n\n" . preg_replace('/^(SELECT( DISTINCT)?)/i', '\\1 ROW_NUMBER() OVER(' . trim($orderby) . ') AS ' . $this->escape_identifiers('CI_rownum') . ', ', $sql) . "\n\n) " . $this->escape_identifiers('CI_subquery') . "\nWHERE " . $this->escape_identifiers('CI_rownum') . ' BETWEEN ' . ($this->qb_offset + 1) . ' AND ' . $limit;
        }
        
        return preg_replace('/(^\SELECT (DISTINCT)?)/i', '\\1 TOP ' . $limit . ' ', $sql);
    }
    
    // --------------------------------------------------------------------
    
    /**
     * Insert batch statement
     *
     * Generates a platform-specific insert string from the supplied data.
     *
     * @param string $table            
     * @param array $keys            
     * @param array $values            
     * @return string|bool
     */
    protected function _insert_batch($table, $keys, $values)
    {
        // Multiple-value inserts are only supported as of SQL Server 2008
        if (version_compare($this->version(), '10', '>=')) {
            return parent::_insert_batch($table, $keys, $values);
        }
        
        return ($this->db->db_debug) ? $this->db->display_error('db_unsupported_feature') : FALSE;
    }
    
    // --------------------------------------------------------------------
    
    /**
     * Close DB Connection
     *
     * @return void
     */
    protected function _close()
    {
        sqlsrv_close($this->conn_id);
    }
}
